Non-invasive monitoring of transient and stable gene expression would be a potent technique to evaluate normal and pathological processes as well as the efficacy of disease treatment. The "biosensor" proposed will take advantage of well known early patterns of gene transcription which occur in response to pathologic stimuli. Promoter sequences of native genes that are transcriptionally activated in ventricular myocardium under pathologic conditions will drive expression of an NMR sensitive reporter gene. This DNA sequence will be transfected and characterized in isolated cells to establish its patho-sensitivity. Subsequently, these constructs will be used to create transgenic mice for in vivo studies. Detection of the biosensor will require novel NMR RF microcoils of two general designs: 1)planar or cylindrical geometry amenable to isolated cell conditions and 2) an interventricular catheter coil of solenoid or Maxwell design. Since both the reporter and detectors are being developed simultaneously, the result will be a truly integrated detection system. Specific Aim I. - NMR Sensitive Reporter Genes and Transfection into Cardiocytes: Hypothesis 1: Endogenous genes and gene products can be combined to non-invasively monitor cellular status. Hypothesis 2: Specifically engineered cells can act as endogenous biosensors of physiological stress. Specific Aim II. - Mouse Cardiac Catheter MR Microcoil: Hypothesis: A MR cardiac catheter microcoil can detect localized 31P NMR spectra from inside the mouse ventricle. Specific Aim II1. - Cell Culture Microcoil: Hypothesis: A MR microcoil can detect gene expression defined 31P NMR spectra from isolated cells or cell lines. Specific Aim IV. - Endogenous Biosensors Expressed in Hearts of Transgenic Mice: Hypothesis: NMR sensitive reporters (Biosensors) can be expressed and detected in the heart of a mouse in response to transient and stable hypertrophic stimuli. The importance of this approach suggests it is now possible to provide a very early detection of intracellular events prior to tissue remodeling or mechanical failure. This opens the window to early treatments such that a reversal of the process is possible. This system will also be able to evaluate therapeutic regimens as the activity of the biosensor (CK) will modulate with the disease process.